Field of the Invention
This invention relates to a water-absorbent resin composition, an absorbent material, and an absorbent product, and a method for the production of the water-absorbent resin composition. More particularly, this invention relates to a water-absorbent resin composition, an absorbent material, and an absorbent product which exhibit excellent hygroscopic and fluid property, separation-resistant property, deodorizing property, gel strength and absorbent property, when used as sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads. This invention further relates to a method for the production of a water-absorbent resin composition possessing such characteristics.
Description of the Related Art
The water-absorbent resin is extensively used in such sanitary materials as disposable diapers, sanitary napkins, and incontinence pads with the object of absorbing such humors as urine and blood and form main components of such sanitary materials as these.
In recent years, in consequence of growth in the demand for adult disposable diapers owing particularly to the aging of the society, the desirability of imparting a deodorizing property, particularly a deodorizing property capable of eliminating offensive odors originating in such sulfur type compounds as hydrogen sulfide and mercaptans, to the water-absorbent resin has been finding growing recognition.
As a means to impart the deodorizing property to the water-absorbent resin, the combinations of the water-absorbent resin with various kinds of deodorants and antibacterial agents have been proposed. For example, a water-absorbent resin composition comprising a water-absorbent resin and the extract of leaves of the trees of theaceous plant (refer to JP-A-S60-158861, for example), an adsorbent resin composition containing the extract of coniferous trees and a water-absorbent resin possessing a specific performance (refer to JP-A-H11-241030, for example), a deodorizing resin composition having zeolite particles dispersed in a water-absorbent resin (refer to U.S. Pat. No. 5,980,879, for example), a water-absorbent resin composition formed of a water-absorbent resin and a metal-containing hydroxide comprising one element selected among titanium and zirconium and at least one element selected among zinc, aluminum, calcium, magnesium, and silicon (refer to JP-A-H10-147724, for example), a water-absorbent resin composition formed of a water-absorbent resin, an oxalate compound, and a complex silicate compound (refer to JP-A-H10-298442), a water-absorbent resin composition formed of a water-absorbent resin, a tannate, and a complex silicate compound (refer to JP-A-H11-116829, for example), a water-absorbent resin composition formed of a water-absorbent resin, a glycine type amphoteric surfactant, and a complex silicate compound (refer to JP-A-H11-49971, for example), and a water-absorbent resin composition formed of a water-absorbent resin, a sulfur-containing reducing agent, and a complex silicate compound (refer to JP-A-H11-148023, for example) have been known.
Methods for imparting a deodorizing property to absorbent products using a water-absorbent resin also have been studied. For example, an absorbent product formed of refined tea and a water-absorbent resin (refer to JP-A-H2-41155, for example), a disposable diaper containing a water-absorbent resin and a resin formed of benzalkonium chloride and/or chlorohexidine gluconate (refer to JP-A-S63-135501, for example), and a sanitary store combining a water-absorbent resin and zinc aluminosilicate (refer to JP-A-S64-5546, for example) have been known. The feasibility of imparting a deodorizing property and a powder handling property both to a water-absorbent resin also has been studied. For example, an absorbent agent formed of a water-absorbent resin, a compound possessing an antibacterial function against an ammonia-producing microbe, and a pharmaceutical preparation manifesting a neutralizing ability or a neutralizing ability and an adsorbing ability to ammonia (refer to International Publication WO00/01479) has been known. As concerns the water-absorbent resin, the improvement in the hygroscopic and fluid property (the improvement in the anti-caking property) forms an important task besides the impartation of a deodorizing property and an anti-bacterial property to the water-absorbent resin. To be specific, the water-absorbent resin has the problem of losing fluidity as powder and entailing the phenomenon of blocking during the course of absorbing humidity. The pamphlet of International Publication WO00/01479 also discloses a technique of using various additives for the purpose of solving this problem.
The deodorizing property produced by any of the aforementioned hitherto reported methods is not so great as to reach the level of manifesting a fully satisfactory deodorization in actual use. When the water-absorbent resin sacrifices the absorbent property thereof for the sake of enabling the deodorizing property thereof to be manifested to a high degree, it does not achieve the inherent object of absorbing such humors as urine and blood.
It is, therefore, an important rule to have the absorbent property exalted to a fully satisfactory level while having the deodorizing property manifested to a high degree as well.
When the water-absorbent resin incorporates additives therein for the purpose of enhancing the deodorant property and the hygroscopic and fluid property, it possibly entails such adverse phenomena as separation and exfoliation where the additives are in the form of powder. When the separation or exfoliation of such additives occurs, the additives entail formation of dust and fail to manifest the function thereof fully satisfactorily.